docs: def _get_all_lengths(self):
          """ For every utterance, get the length of the data in every container. Return a list of tuples. """
          utt_lengths = {}
  
          for utt_idx in self.utt_ids:
              per_container = [c._file[utt_idx].shape[0] for c in self.containers]
              utt_lengths[utt_idx] = tuple(per_container)
  
          return utt_lengths